Harsh Kumar Verma
Advisors: Prof. Blair Brettmann and Prof. Josiah Hester

will defend a master’s thesis entitled,

Sound Sensing BATS – Biodegradable Acoustic Triboelectric Nanogenerator Sensors

On

Monday, April 08 at 1:00 p.m.

RBI Room 114

Committee
            Prof. Blair Brettmann – School of Materials Science and Engineering, Georgia Tech (Co-advisor)
            Prof. Josiah Hester – School of Interactive Computing, Georgia Tech (Co-advisor)
            Prof. Nivedita Arora – Department of Electrical and Computer Engineering, Northwestern University
            Prof. Antonio Facchetti – School of Materials Science and Engineering, Georgia Tech

Abstract

Two of the prominent challenges facing modern development of electronic devices are minimizing their power requirements and simplifying the disposal processes. Recent developments in self-powered energy harvesters such as triboelectric nanogenerators (TENGs) have been extensively focused on the use of more environmentally sustainable materials to minimize the environmental impact while being able to harvest energy from the environment. In this thesis, I have investigated 3 different versions of biodegradable triboelectric nanogenerators for acoustic energy harvesting, referred to as biodegradable acoustic triboelectric nanogenerator sensors (BATS).

To study the negative layer, I use a tribonegative biopolymer, poly (L-lactic acid) and compare the voltage outputs of the device to traditional materials such as FEP. These results indicated good usability of PLLA based BATS, albeit an order of magnitude lower signal than for FEP based BATS. I also examined how the polymer crystallinity and volatile content in the PLLA films impacts the performance. To study the positive layer, I selected silk fibroin as a tribopositive biopolymer. Variation in voltage output was observed and correlated to changes in drying temperature and the water uptake of the polymer, demonstrating the dependence of the TENG performance on the dynamic behavior of the biopolymers and the environmental conditions. Lastly, I used a contact separation mode for the TENG and examined the combined effects of the triboelectric biopolymers PLLA and silk fibroin on the TENG performance.  A shift in the resonant frequency was observed in these devices over time due to the hygroscopic property of both PLLA and silk fibroin. As in the previous cases, the reduction in voltage was observed and correlated with the reducing residual solvent in the films over time.

Overall, residual solvent after processing and water absorption, measured by changes in the volatile content of the polymer, were found to be a major factor significantly affecting the properties of the triboelectric layers. Optimizing the processing conditions and the solvents used for these polymers is crucial, as this not only affects their triboelectric property but also, the changes in TENG performance over time.